The present invention relates to a device for and a method of administering a medication into epidural space.
During the last decade the regional block analgesia (spinal and epidural) achieved widespread popularity among anesthesiologists. The region block provided excellent analgesia and muscle relaxation during surgical procedure. In addition it is also beneficial to the patients in postoperative period, as well as to some patients suffering from pain of different etiology. It is generally accepted that epidural block has many advantages compared to the spinal: absence of headaches and relatively gradual and delayed hypotension are just some of them. The main problem with epidural block is the difficulty of accurate identification of the epidural space, which may explain occasional failure of this type of analgesia. To identify the epidural space most anesthesiologists use the so-called method of loss of resistance to injection. The method based on the fact that the piston of the syringe, filled with air or fluid, meets resistance and bounces during the injection attempt, when the bevel of the needle is located in the rigid tissues superficial to the epidural space, especially ligamentum flavum. When the bevel of the needle reaches the epidural space, the piston of the syringe has to move easily due to the loss of the resistance to injection. In the practice it is not always so obvious due to some drawbacks of the described method.
The above described method has the following drawbacks:
1. The method is not completely objective. Using this method the practitioner in a great degree relies on his own experience and his individual ability to sense changes in pressure. Both these qualities are rather subjective. Therefore, in not very clear cases of loss of resistance, practitioners may have different opinions regarding correct placement of the epidural needle.
2. The movement of the piston along side the walls of a syringe by itself meets some resistance, especially significant, if during the advance of the epidural needle some blood enters the syringe. In these instances it is very difficult to recognize the loss of resistance. As a result the epidural needle may be placed in the subarachnoid space with all of the undesirable consequences: severe headaches in postoperative period or if the misplacement of the needle is not recognized immediately and the local anesthetic administered, total spinal block--a very dangerous life-threatening complication.
3. This method requires use of a needle of a big diameter. As a matter of fact all epidural sets available contain only #17 or less often #18 gauge needles. Introduction of these needles may not be very pleasant to the patients.